The state of the art is exemplified by the following references: Gottschalk U.S. Pat. No. 5,495,738; Gottschalk, et al. U.S. Pat. No. 5,445,003; Bone U.S. Pat. No. 5,493,761; Wilkens U.S. Pat. No. 5,138,859; Betsrein U.S. Pat. No. 4,561,276; Ostertag U.S. Pat. No. 4,947,668.
In many modern day automobiles, engines are downsized for installation into relatively smaller new vehicles. Other automotive components such as crankshafts and camshafts are being downsized to accommodate smaller engines, as well as to reduce weight and improve fuel efficiency. This downsizing of components can sometimes result in compromises in strength and durability, as compared with older, larger engine components. In particular, there is a need to improve the strength and durability of downsized crankshafts. The fatigue strength and durability of crank pins and main bearing journals can be significantly increased by various manufacturing processes.
A wide variety of machines and processes is known in the art for strengthening and finishing metallic work pieces such as crankshafts and camshafts. In particular, it is known to “deep roll” or press an annular groove about the circumference of a crankshaft at points where a cam lobe joins with the shaft. In a typical process, a crankshaft or similar elongate workpiece is engaged with a deep rolling tool. Force is applied to press a roller of the tool, known in the art as a “work roll,” against the shaft of the crankshaft as the crankshaft is rotated. The force of the work roll causes compressive stresses on the shaft, deforming the shaft circumferentially, and forming an annular groove therein. In one example of such an application, the work roll(s) is/are applied in the middle of the annular fillets between the pin journals and adjacent counter weights or balancing webs. Such deformation or pre-stressing of the crankshaft/camshaft has been shown to significantly improve the strength and/or durability of the workpiece.
Known processes/assemblies often utilize a single upper, deep rolling tool, positioned opposite a “lower tool.” The purpose of the lower tool is to support the side of the shaft opposite the point at which the force is applied via the work roll(s). These systems have worked quite well over the years, however, utilizing two separate types of tool, i.e. the deep rolling tool and the lower tool, for carrying out the deep rolling process is not without drawbacks. Various lower tool designs are known in the art, however many known designs are relatively complex. The use of separate tools can also require separate maintenance, inspection, repair and cleaning tasks for each tool. Moreover, in conventional designs having a single deep rolling tool, one complete turn of the workpiece shaft is necessary to apply the work roll against the entire circumference of the shaft to be treated, sometimes necessitating many, relatively time-consuming rotations of the shaft before the workpiece is suitably processed. Even modest improvements in design and processing efficiency are often welcomed by the industry.
It is an object of the present invention to provide a novel design for improving deep rolling tool performance and processing time.
Other objects, features and advantages of the present invention will become apparent upon an examination of the accompanying drawing figures, following detailed description and appended claims.